Monday, June 18, 2007 - 11:00 AM

Effect of Harvest Timing on Corn and Forage Sorghum Production Under Limited Irrigation.

Mark Marsalis, New Mexico State University-ASC at Clovis, 2346 State Road 288, Clovis, NM 88101

Water resources in eastern New Mexico are declining rapidly and current agricultural practices in the region are not sustainable. Forage sorghum (FS) may provide an acceptable alternative to corn grown for silage as irrigation well capacities continue to reduce. It is uncertain what the effects of delayed harvest are on yield and nutritional aspects of FS and corn when grown with a limited amount of water. A 2-yr study was initiated at the NMSU Agricultural Science Center at Clovis in 2005 to investigate the effects of harvest timing on corn and forage sorghum yield and quality. Crops used were corn, conventional forage sorghum (C-FS) and brown midrib forage sorghum (BMR-FS).  Irrigation amount was 33 mm wk-1 and was equivalent to a well capacity of 96.5 m3 hr-1 on 48.6 ha. Crops were harvested at 2 moisture contents: optimum (60-65%) and late (50-59%). Conventional FS produced more dry matter than corn and BMR-FS when harvested at optimum stage (C-FS, 21.1 Mg ha-1; corn, 18.2 Mg ha-1; BMR-FS, 16.9 Mg ha-1); however, yields for C-FS and corn were similar at late harvest. Yields of both FS declined rapidly to late harvest. Net energy for lactation (NEl) and total digestible nutrients (TDN) were reduced at late harvest for all crops, especially C-FS. BMR-FS maintained similar TDN to corn, even when harvested at moisture levels lower than 60%; NEl for both FS were lower than that of corn. Results support previous research indicating that forage sorghums are more water-use efficient than corn; however, allowing FS to stand in the field beyond optimum moisture content reduces yield and nutritive value to a greater extent than corn.

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